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    <title>Document</title>
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<script>
    //声明一个set
    let s =new Set();
    let s2=new Set(['大事不好',"大海","沙漠","森林"])

    //元素个数
    s2.add('冰原')
    s2.delete('大事不好')
    s2.has('大海')
    s2.clear()
    console.log(s2, s2.has('大海'))

</script>
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